This application claims priority from Korean Patent Application No. 2004-80593 filed Oct. 8, 2004 incorporated herewith by reference in its entirety.
1. Field of the Invention
The present invention relates to a field coil assembly of an electromagnetic clutch for a compressor, and more particularly, to a field coil assembly of an electromagnetic clutch for a compressor, in which a coil wire of an electromagnetic coil body exposed to a protrusion of a bobbin is electrically connected with a compressing portion of a coil wire formed at one side end portion of terminals mounted inside a sleeve, and the terminals and the electromagnetic coil body are molded with the resin, thereby preventing permeation of foreign matters from the outside, preventing disconnection of the coil wires due to vibration, and simplifying a manufacturing process.
2. Background Art
In general, a field coil assembly of an electromagnetic clutch for a compressor is an electric device for transferring driving force of a pulley rotated by an engine to a hub disc of a compressor driving shaft by forming a magnetic field by electromagnetic induction of a wound coil when electric power is supplied and sucking the hub disc of the compressor driving shaft toward a friction surface of the pulley by magnetic force for accomplishing a dynamic connection. In addition, the field coil assembly of an electromagnetic clutch for a compressor serves to control operation of a cooling system of an air conditioning apparatus by regulating driving force of the compressor according to whether or not electric power is supplied to the coil.
FIG. 1 is a partially sectional view showing an example of a conventional electromagnetic clutch for a compressor.
As shown in the drawing, the electromagnetic clutch includes: a pulley 1 dynamically connected to a crank shaft of an engine by a driving belt (not shown) and having a friction surface 1a on a side surface thereof; a field coil assembly 2 embedded in the pulley 1, supported by a housing 4 of the compressor, and generating a suction magnetic flux when electric power is supplied; and a disc and hub assembly 3 connected to a driving shaft 4a of the compressor by a hub 3a and sucking a disc 3b to the friction surface 1a of the pulley 1 by the suction magnetic flux generated by the field coil assembly 2 in order to transfer driving power of the engine to the driving shaft 4a of the compressor.
In the conventional electromagnetic clutch, when the electric power is supplied to the field coil assembly 2, the disc 3b is moved toward the pulley 1 rotated by the belt connected to the crank shaft by the suction magnetic flux due to magnetic induction of the electromagnetic coil and a friction surface of the disc 3b is sucked to the friction surface 1a of the pulley 1 so as to connect the pulley 1 and the disc 3b, whereby the driving force of the engine transferred to the pulley 1 through the belt is transferred to the driving shaft 4a of the compressor through the disc 3b and the hub 3a. 
When the power supply to the electromagnetic coil is shut off, the disc 3b is separated from the friction surface 1a of the pulley 1 by an elastically repulsive force of an elastic member 3c, whereby it is prevented that the driving force of the engine is transferred to the driving shaft 4a of the compressor.
As described above, the electromagnetic clutch of the compressor transfers or shuts off the driving force of the engine to or from the compressor according to whether or not the electric power is supplied.
The field coil assembly for forming the magnetic field on the electromagnetic coil is classified into a hard shell type and an epoxy type.
FIG. 2 is a sectional view showing an example of a conventional field coil assembly of an electromagnetic clutch of a compressor. Referring to FIG. 2, the field coil assembly of the hard shell type will be described.
As shown in the drawing, the field coil assembly 2 includes: an electromagnetic coil body 2a formed by an electromagnetic coil wound in a ring type; a bobbin 2b accommodating the electromagnetic coil body 2a therein and having a protrusion 2b-1 for exposing a pair of coil wires 2a-1, which is drawn out from the electromagnetic coil body 2a, to the outside; a core ring 2c accommodating the bobbin 2b embedding the electromagnetic coil body 2a therein, inserted and mounted into the pulley 1 and fixed on the compressor; and a cover 2d for hermetically sealing an opened surface of the core ring 2c in order to prevent that the electromagnetic coil body 2a and the bobbin 2h are separated from the core ring 2c. 
Furthermore, the bobbin 2b has a terminal insertion slit formed on the protrusion 2b-1, and a mag-mate terminal 5 is inserted into the terminal insertion slit, whereby the protrusion 2b-1 is electrically connected with the coil wire 2a-1.
Moreover, a sleeve 6 mounted on an end portion of a lead wire (not shown) for supplying the external electric power is connected to the protrusion 2b-1.
The sleeve 6 has a diode 7 and a resistor 8 therein, wherein the diode 7 prevents generation of surge voltage and back electromotive force which are generated when electric power applied to the electromagnetic coil body 2a is shut off, and the resistor 8 prevents generation of off noise which is generated due to a closed circuit formed by the diode 7.
However, the field coil assembly 2 of the hard shell type has a disadvantage in that the electromagnetic coil body 2 is corroded due to permeation of moisture through a fine gap formed by the cover 2d and the core ring 2c. 
FIG. 3 is a sectional view showing another example of the conventional field coil assembly of the electromagnetic clutch of the compressor. Referring to the drawing, the field coil assembly of the epoxy type will be described. In FIG. 3, the same parts as the example of FIG. 2 have the same reference numerals as FIG. 2.
As shown in the drawing, the field coil assembly 2 includes: an electromagnetic coil body 2a formed by an electromagnetic coil wound in a ring type and having a coil wire 2a-1 drawn out from both end portions thereof; a core ring 2c of a doubly cylindrical form having a receiving hole for receiving the electromagnetic coil; and an epoxy resin 2e filling the inside of the receiving hole of the core ring 2c in which the electromagnetic coil is accommodated.
The field coil assembly 2 is filled with an epoxy resin 2e in a state where the electromagnetic coil body 2a is coupled with the receiving hole of the core ring 2c, and the epoxy resin 2e is hardened when a predetermined time period is passed.
Furthermore, the diode 7 and the resistor 8 are connected to a lead wire 2a-2 connected to an end portion of the coil wire 2a-1 drawn out from the electromagnetic coil body 2a in parallel. At this time, lead lines extended to sides of the diode 7 and the resistor 8 are welded mutually and connected in series, and lead lines extended to the other sides of the diode 7 and the resistor 8 are spliced to the lead wire 2a-2.
Moreover, first, the spliced portion is covered with a first covering material (a) for protection and insulation from the outside, and next, the diode 7 and the resistor 8 are covered with a second covering material (b), and finally, the second covering material (b) is covered with a third covering material (c).
However, the field coil assembly of the epoxy type has several disadvantages in that it takes much time to install the diode 7 and the resistor 8, in that a manufacturing process is too complicated, and in that assembly efficiency is lowered.
Meanwhile, as a prior art, Japanese Patent Publication No. 1995-127663 discloses a method for connecting a spool and terminals in a connector integrated stator of an electromagnetic clutch. In Japanese Patent Publication No. 1995-127663, the method for coupling the spool and the terminals include a method for integrally injection-molding the connector.
The method for integrally injection-molding the connector includes steps of connecting terminals to a coil wire, and molding resin to integrally mold a connector body. However, the prior art also has several disadvantages in that an error rate rises since the connector of a complex shape is integrally injection-molded, and in that the coil wire and the terminals may be transformed by a high injection pressure since even the connector body is integrally injection-molded.
Additionally, the prior art has other disadvantages in that an assembly process and an injection process of the coil wire and the terminals are very complicated, and in that productivity is lowered since it is difficult to install a surge prevention element.